Production of growth centers in roots and stems of chaparrals: Implications to revival after fires

Abstract

Chaparral vegetation occurs in Mediterranean regions with warm summers, moderate winters, and limited rainfall during winters. In California, chaparral vegetation comprises 1% of natural vegetation; 20% of all plant species for the state. Chaparral plants are short, woody plants without a single tap root and trunk. For four chaparral species of this study, axis splits occurred between 30 mm below the transition zone to 30 mm above the transition zone. Axis splits and the tissues that resulted from axis splits were identical in roots and stems. All four species showed extensive lobes that produced anomalous growth patterns. In both roots and stems, axis splits partitioned the original vascular cambium and produced fragmented cambial cells and eventually growth centers. Growth centers produced independent roots and stems. Fragmented cambia are deep in tissues and may be moved during growth processes and produce growth centers months to years later. Moreover, deep-seated growth centers may produce roots and stems in individual chaparral plants after fires. To our knowledge this is the first report to demonstrate: (1) axis splits and fragmented cambia occur in chaparral shrubs, (2) axis splits are identical in roots and stems, (3) the production of growth centers by axis splits and fragmented cambia form roots and stems at transition zones, and (4) the production of growth centers may be involved in the revival of individual plants after fires.